When the stimulable phosphor is exposed to radiation such as X-rays, it absorbs and stores a portion of the radiation energy. The stimulable phosphor then emits stimulated emission according to the level of the stored energy when the phosphor is exposed to electromagnetic wave such as visible light or infrared rays (i.e., stimulating light).
A radiation image recording and reproducing method utilizing the stimulable phosphor has been widely employed in practice. The method employs a radiation image storage panel comprising the stimulable phosphor, and comprises the steps of causing the stimulable phosphor of the storage panel to absorb radiation energy having passed through an object or having radiated from an object; sequentially exciting the stimulable phosphor with a stimulating light to emit stimulated light; and photoelectrically detecting the emitted light to obtain electric signals giving a visible radiation image. The storage panel thus treated is subjected to a step for erasing radiation energy remaining therein, and then stored for the use in the next recording and reproducing procedure. Thus, the radiation image storage panel can be repeatedly used.
The radiation image storage panel (often referred to s stimulable phosphor sheet) has a basic structure comprising a substrate (i.e., support) and a stimulable phosphor layer provided thereon.
The stimulable phosphor layer is conventionally formed by coating a dispersion of phosphor particles in a binder solution on the substrate and drying the coated dispersion on the substrate, and therefore comprises a binder and phosphor particles dispersed therein.
It is desired that radiation image storage panels used in these methods have sensitivity as high as possible and further can give a reproduced radiation image of high quality (in regard of sharpness and graininess).
It is known that a radiation image storage panel having on a substrate a stimulable phosphor layer prepared by gas phase deposition such as vacuum vapor deposition or sputtering has a stimulable phosphor layer comprising multiple prismatic (or pillar-shaped) stimulable phosphor crystals standing on the substrate, and gives a reproduced radiation image with high sensitivity as well as high sharpness.
Japanese Patent Publication No. 61-245099 describes a radiation image storage panel in which prismatic stimulable phosphor crystals comprising at least two layers are arranged an a support.